33. A substance derived from the Madagascar periwinkle, which has proved useful in decreasing mortality among young leukemia patients, is cultivated in China as part of a program to integrate traditional herbal medicine into a contemporary system of health care.

(A) A substance derived from the Madagascar periwinkle, which has proved useful in decreasing mortality among young leukemia patients,

(B) A derivative, which has proved useful in decreasing mortality among young leukemia patients, of the Madagascar periwinkle,

(C) A Madagascar periwinkle derivative, which has proved useful in decreasing mortality among young leukemia patients,

(D) The Madagascar periwinkle has a derivative which has proved useful in decreasing mortality among young leukemia patients, that（E）

(E) The Madagascar periwinkle, a derivative of which has proved useful in decreasing mortality among young leukemia patients,

如果选E的话，我觉得原文的意思就变了。文中说的是a derivative of the madagascar periwinkle是传统与现代的结合，, 但是E 说的是M本身是传统草药与现代医疗的结合。

所以我选了C。 derivative,也有名词的意思-衍生物。

请指教！

A derivative can be manufactured, extracted but cannot be cultivated.

A plant can be cultivated.

你可以提取衍生物,种植植物,但不可以提取植物,种植衍生物.

In this case, the meaning of the sentence is that a kind of plant grow in china and this plant can be used to produce certain derivatives. So the subject has to be the plant when the verb is 'be cultivated'.